1. Field of the Invention
The present invention relates to a rotary electric machine having an improved fixing structure for teeth of a stator of the rotary electric machine, and also relates to an electric wheelchair (or electrically powered wheelchair) mounted with such rotary electric machine.
2. Related Art
In a known art, as such a rotary electric machine, there has been provided an axial gap type rotary electric machine as shown, for example, in FIGS. 16 to 19.
Referring to FIGS. 16 to 19, the rotary electric machine is provided with a stator 3 formed with teeth 2 and a rotor provided with a plurality of magnets (permanent magnets), not shown, in which the stator and the rotor are arranged with a gap in a rotation axis direction.
More in detail, as shown in FIG. 18, the each tooth 2 is composed of a plurality of steel plate sheets 2a laminated in a radial direction thereof for a countermeasure to core loss, and a plurality of such teeth 2 are arranged and fixed side by side with a predetermined distance in the circumferential direction of a disc, i.e., substantially ring-shaped, stator yoke core 6. Coils 5 are wound up around these teeth 2 through insulating material as bobbins 4. Further, as shown in FIG. 19, the teeth 2, the stator yoke core 6 and the coils 5 are integrally fixed by means of molding resin 7 such that surfaces 2b of the teeth 2 opposing to the rotor are exposed.
The steel plates 2a of the teeth 2 are assembled separately into a fitting hole of the stator yoke core 6 and then molded and fixed together by means of molding resin 7.
However, in such arrangement, because the molding resin 7 does not reach a portion surrounded by the bobbins 4, it was difficult to firmly fix the teeth 2.
Incidentally, the teeth 2 are attracted by magnets disposed so as to oppose to the teeth, and the attracting force of the magnet acts in an arrowed direction A in FIG. 19, so that it is necessary to consider a countermeasure for preventing the teeth 2 from coming off.
Then, it has been provided, as a method for preventing such coming-off of the teeth, to firmly push and fix the teeth 2 into a stator yoke core 6 or to fix the teeth by welding means.
In another method such as disclosed in the Japanese Patent Application Laid-open Publication No. HEI 11-146617, a notch is formed by means of punch to be fixed.
However, in such conventional methods, when the tooth 2 is pushed into the fitting hole of the stator yoke core 6 and then fixed thereto or is welded to thereby increase contacting strength therebetween, there is a fear that an electric resistance at this fixed portion is reduced and a closed circuit is formed around the fitting hole in a plan view, resulting in energy loss due to large induction current flow.
In addition, in the method of using the punch, a fixing process using the punch will be additionally required, and moreover, the use of the punch will give an adverse impact, thus being troublesome and inconvenient for dimensional control.